Silicone oils are widely used in cosmetic preparations, since they are colorless, odorless and chemically and physiologically inactive. Particularly, high-viscosity organopolysiloxanes are often used in hair cosmetic preparations, since they are capable of adhering to the hair in a favorable manner.
However, when directly emulsifying a high-viscosity organopolysiloxane, the average particle diameter of the emulsion particles can only be as small as about several micrometers, and a finer average particle diameter cannot be easily obtained, thus resulting in a low emulsion stability.
For this reason, various studies have been made on a method for producing an emulsion through emulsion polymerization, for the purpose of obtaining fine emulsion particles and thus improving the stability of the emulsion. For example, there has been known a method for performing emulsion polymerization on an emulsified cyclic siloxane oligomer, using a strong acid or a strong base (Patent documents 1, 2 and 3). However, in each method, octamethylcyclotetrasiloxane will be produced in an emulsion in an amount of not smaller than 1,000 ppm by mass. Thus, when adding such emulsion to a cosmetic preparation, there occurs a problem that the stability and feel will be impaired.
Further, octamethylcyclotetrasiloxane has been considered as a substance of concern in recent years, and cosmetic preparations containing a restricted amount of octamethylcyclotetrasiloxane have been demanded.